PURPOSE: The term 'mesiodens' refers to a supernumerary tooth present in the midline of the maxilla between the two central incisors. This study seeks to investigate the characteristics of mesiodens among children in Korea. METHODS: The study population consisted of 40 children whose ages ranged from 4 to-26-years. The characteristics of mesiodens were obtained from radiographs and clinical examination results, and were confirmed by surgical intervention. RESULTS: Results showed that males were affected approximately 4 times as frequendy as females. Twenty-five percent of the patients had more than 1 supernumerary tooth. About 66% of the mesiodens were conical in shape and about 52% of the mesiodens were in the upward position. The age and sex distribution, number of mesiodens per patient, shape, direction, size, and effect on permanent maxillary incisors are also presented in this study. CONCLUSIONS: The incidence of mesiodens has been estimated at 0.15% to 1% of the population. It occurs more frequently in boys than in girls, with the ratio being approximately 2:1. In this study, a male:female ratio of 4:1 for the prevalence for mesiodens was found. Ten (25%) out of the 40 patients had 2 mesiodens.